1. Field of the Invention
The present invention relates to motor vehicle safety apparatus, and particularly to devices which prevent deployment of an air bag relative to out-of-position occupants in order to prevent serious or fatal injury to such occupant of the vehicle.
2. Description of the Related Art
Over the years many safety devices have been developed to reduce the number of fatalities and serious injuries resulting from motor vehicle accidents. The seat belt marked a major milestone in the development of vehicular safety devices, but because of perceived inadequacies in the use of seat belts alone, the trend in the current decade has been towards supplementing seat belts with air bags. While air bags have been credited with saving lives, air bags have also been implicated as the cause of many serious injuries and deaths.
Among other problems with air bags, they may deploy when the occupant of the seat is too far forward, and hence too close to the air bag cover and air bag, either through the explosive force resulting from the rapid inflation and deployment (an air bag can inflate in milliseconds) of the air bag, or through a smothering effect. Air bags have traditionally been designed based upon the position of the average male relative to the steering wheel of the vehicle. Individuals who are shorter than average, or who have shorter legs, may actually adjust the seat to sit farther forward, while taller individuals, or those with longer legs, may adjust the seat to sit farther back, so that the driver's actual sitting position may vary from six to twelve inches closer or farther to the steering wheel than the average male. Similar considerations may apply to the occupant of the passenger's seat.
A complicating factor is the use of seat belts, which is highly recommended with the use of air bags. Older seat belts consisted of a strap which buckled around the waist of the occupant of the seat. Modern seat belts are supplements with a shoulder harness and a pretensioner system which automatically pulls the occupant back in the seat in the event of a collision. If, however, the occupant is not wearing a seat belt, the occupant may be thrown far forward before the air bag receives the appropriate signal to deploy from a crash sensor, leaving the occupant to be buffeted between the force of the crash snapping him forward, and the force of the air bag exploding as it inflates to force him backwards, potentially whipping the neck and spinal column.
Several devices have been designed to help deal with these problems and to improve air bags generally. One approach has been to equip the air bags with a manual switch, leaving the occupant of the vehicle's seat to determine whether to leave the air bag activated. An example of this approach is shown in U.S. Pat. No. 5,544,914, issued Aug. 13, 1996 to Borninski, et al. Borninski shows a circuit to manually disable the air bag with a key switch. A second approach is exemplified by sensor circuits designed to automatically deactivate the air bag based upon electronic sensing of the occupant's seat position. An example of this type of apparatus is described in U.S. Pat. No. 5,653,462, issued Aug. 5, 1997 to Breed, et al. The Breed Patent describes the use of ultrasonic, electromagnetic, and infrared sensors to detect the position of the occupant relative to the seat Breed's apparates includes a device for sensing the seat position by a potentiometer with a sliding brush attached to the seat track to prevent deployment of the air bag if the seat is too far forward.
A similar system for sensor detection of passenger occupancy and position employing a combination of thermal and acoustic or ultrasound sensors generating signals which are fused and evaluated by a probability algorithm is disclosed in U.S. Pat. No. 5,482,314, issued Jan. 9, 1996 to Corrado, et al.
A slightly different system for linking deployment of the air bag to the status of the seat belt is described in U.S. Pat. No. 5,590,904, issued Jan. 7, 1997 to Ellis, et al. The Ellis patent shows a seat belt buckle switch connected to a resistor network sending a first signal to a microprocessor controller if the buckle switch is closed and a second signal if the buckle is open. The controller evaluates whether to deploy the air bag basted upon the state of the signal.
Various circuits for determining that the air bag should be deployed are described in U.S. Pat. No. 5,629,847, issued May 13, 1997 to Shirakawa, et al. (system evaluates two acceleration signals, or acceleration and deceleration signals, to evaluate whether to deploy air bag) and U.S. Pat. No. 5,631,834, issued May 20, 1997 to Tsurushima, et al. (control circuit for judging the magnitude of a collision, connecting a power source to an igniting device to activate the air bag).
Devices to prevent the air bag circuitry from malfunctioning include U.S. Pat. No. 5,506,775, issued Apr. 9, 1996 to Tsurushima, et al. (power source circuit for boosting the battery voltage used to charge the capacitor which ignites the squibs in the event of an accident); U.S. Pat. No. 5,638,274, issued Jun. 10, 1997 to Konishi, et al. (circuit for preventing reset of charging circuit for a back-up power capacitor due to electrical noise, ensuring the capacitor will only be charged when the ignition switch is turned on); and U.S. Pat. No. 5,668,52, issued Sep. 16, 1997 to Kitao (a device which includes a series circuit of squibs connected by bridge wires which ignites the squibs so quickly the air bags will deploy even if a squib opens to create an open circuit). The Kitao patent also includes a device to indicate whether a passenger is present, either means for judging whether the seat belt is locked, a manually operated switch, or a photoelectric, ultrasonic or pressure sensor.
The device of the present invention adds a circuit, or portion of a circuit, between the power source and the squib which activates the inflator to inflate the air bag. The circuit includes a seat adjustment limit switch and a seat belt switch in series with the power source and the squib, so that if the seat is adjusted too far forward, or if the seat belt is unbuckled, the air bag will not deploy.
The Ellis patent, while it deactivates the air bag if the seat belt is unbuckled, makes no provision for preventing deployment if the seat is too far forward. The Breed patent, while it disables the air bag if the seat is too far forward, makes no provision for the unbuckled seat belt. Both devices rely on complicated circuitry with microprocessor evaluation processes, while the device of the present invention operates in a fail-safe manner after the fashion of a circuit breaker.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus air bag deployment inhibitors solving the aforementioned problems are desired.